<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>A出现的次数</title>
		<script>
			var ar=["Abc","cnanada","Australia","Flank","dog"];
			var count=0;
			for(let a of ar){
				if(a.toLowerCase().indexOf("a")>=0)
				   count++;
			}
			document.write("<h1>出现了 "+count+" 次</h1>");
		</script>
	</head>
	<body>
	</body>
</html>